Should DB errors 555 and 558 be adapted for julian/gregorian calendar?

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This is inspired by the result of an error report run on King Charles VIII of France (Valois-273)

Many pre-1600 profiles with a Wikidata counterpart trigger errors 555 and/or 558, obviously because one profile uses the Gregorian calendar and the other uses the Julian one, resulting in a (roughly) 10 days difference between the dates.

I understand Wikitree policy is to use Gregorian dates whenever possible. I don't know about Wikidata. Some dates entered into Wikitree may be Julian where they should be Gregorian, but I'm not sure. Right now I tend to tag those errors False when they concern a profile before 1600 (roughly) and the difference is about 10 days, with a comment like "Julian/Gregorian calendar ambiguity".

Could the error report be adapted to avoid raising false errors, or a more comprehensive explanation added to the help page for these two errors? I'm not sure what the appropriate solution is and of course the issue is complex since countries switched to Gregorian at different periods (beware of Wikidata dates imported from Russian Wikipedia !). Here is a list: https://en.wikipedia.org/wiki/List_of_adoption_dates_of_the_Gregorian_calendar_per_country

Well. Wikidata has 9 July for Charles VIII and Wikitree has 30 June. The difference is the same for his DOD.

But, if Wikitree used the Gregorian calendara and Wikidata the Julian one, it should be the other way around (i.e. the Julian calendar is roughly 10 days behind the Gregorian one - for this period). Correct?

I'm confused. One thing is certain; the pre-requisite for this to work is to know which calendar your source is using.

I don't think Père Anselme says which calendar he is using, but it's very unlikely he would have converted pre-1582 dates to a proleptic Gregorian calendar though.

There is some evidence: we know for certain that his dates match those recorded by Louise de Savoie for the births of her grandchildren. Louise was recording contemporary events and could not have used another calendar than Julian. (Louise's diary, quoted in Medieval Lands, vs. Anselme's works accessed through Gallica).

I'll come back to this issue after the Clean-a-thon (my team turns out highly competitive, can't let them down !)

Also when WIkiTree now start comparing dates with other sources like Wikidata we must explain this is a date using calendar xxxx.....

Ps. I have seen at Wikipedia that just to make it clear for the reader they in the text use a Template that you add after the date and then the reader can click on the text and learn what date is used etc.. maybe something for Wikitree... I dont know if someone is pushing this issue....

I mean that all dates (I should say: in "occidental" countries, countries which used a Julian calendar at the time - I'm not talking about Asia...) up to 4/14 October 1582 were recorded at the time using the Julian system (the only one used in Occident at the time AFAIK). And the convention has remained, since then, to keep the julian as official dates. Go to the Wikipedia entries for any notable or royal of that era, you will see that the dates are Julian.

I believe translating those dates (before 15 October 1582) to proleptic gregorian on Wikitree profile pages - on the data fields - would be extremely confusing because anyone looking at the profile who is familiar with the person profiled would say "Ah! But this is wrong! He was born/died/married 10 days before that!".

I have no problem with adding a proleptic Gregorian conversion in the biography, or anything that you suggest above.

All that I'm saying is that, on a pre-1583 profile without more information, the overwhelming odds are that the dates use the JULIAN convention.

Just to make it clear, I would fully support having several calendars available, and indeed it is the only solution to make things clear for the long period (1582-1923) where Julian and Gregorian calendars co-existed.

Oh yes. One thing with the Republican/Revolutionary Calendar is that dates in this format won't be accepted by Wikitree. And there's no ambiguity. On the other hand, several profiles from gedcom downloads have missing dates because the revolutionary format dates were not accepted.

When entering a date from that era (in France, 1793-1806, but the calendar was also used in other parts of Napoléon's empire, like current Belgium and Netherlands, Luxemburg...) I always write out both forms (revolutionary and gregorian) in the biography.